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The 'in-situ' compatibilization for a PET/LCP blend via transesterification reactions in a twin-screw extruder having a very short residence time is investigated through thermal, rheological, and mechanical studies. Inclusion of a small amount of liquid crystalline polymer (LCP) enhanced the crystallization rate of the poly(ethylene terephthalate) (PET) matrix. It acted as a nucleating agent. LCP lowered the blend viscosity above [T.sub.cn] (crystalline-nematic transition temperature), working as a processing aid. However, the addition of dibutyltindilaurate (DBTDL) as a reaction catalyst was found to increase the viscosity of the blends, diminish the size of the dispersed phase, enhance its adhesion with the matrix, and lead to an increase of mechanical properties of two immiscible phases. Hence DBTDL is helpful in producing a reactive compatibilizer by reactive extrusion at the interface of this polyester blend system. The optimum catalyst amount turned out to be about 500 ppm when the reaction proceeds in 90/10 PET/LCP polyester blend systems. Its effect on the mechanical properties is discussed in detail. The structural change of reactive blend was identified by 1H NMR and wide angle X-ray diffraction patterns., INTRODUCTION Thermotropic liquid crystalline polymers (LCPs) exhibit excellent thermomechanical properties and high chemical stabilities (1-4). Over the past twenty years these properties have been extensively studied, with emphasis on the [...]

Ternary blends of poly(p-phenylenesulfide) (PPS), thermotropic liquid crystalline polyesteramide (LCP), and polysulfone (PSF) were investigated in terms of processing characteristics, blend morphology, and physical properties. In the incompatible PPS/LCP blends, LCP imparted a nucleating effect to the crystallization of PPS. Up to 10wt% LCP content, the tensile properties of PPS/LCP blends were enhanced with increasing LCP content, but they deteriorated if the LCP content exceeded 20wt%. Addition of a third component, PSF, to the 90/10 PPS/LCP blend promoted development of rodlike or threadlike fibrillar structure and orientation of the deformed LCP domains, which led to improvement of tensile strength up to 20%., INTRODUCTION Recently the 'in-situ composite forming technique' as been proposed to improve the mechanical properties of general purpose engineering plastics (1). In this technique, the thermotropic liquid crystalline polymer (LCP) [...]

This study investigates deformation of a thermotropic liquid crystalline polymer (TLCP) in different die geometries. Blends of a TLCP with a thermoplastic elastomer of EPDM were made in a twin-screw extruder. Morphological observation of the extruded blends demonstrates the complimentary effect of shear in the die exit on dispersed phase deformation and fibril formation. Shear strain can affect fibril formation for a relatively large dispersed phase in the region close to the die wall. However, the main role of shearing is in breaking up the larger particles and initial polydomain structure. A strong elongational deformation on the blended melt after the die exit is required, and free microfibrils normally observed in in situ composites were not easily formed by shear deformation only in the die., INTRODUCTION Thermotropic liquid crystalline polymers have attracted attention during the past two decades because of their characteristic properties (1-5), one of which is their ability to form self-reinforced blends with [...]

Ternary blends of polyarylate (PAR) U-Polymer 100, thermotropic liquid crystalline copolyester (LCP) Vectra A950, and a block copolyesterether Hytrel 7246 were investigated in terms of rheological properties, morphology, and mechanical properties. The PAR/Hytrel blend exhibited melting point depression and gave a unique single [T.sub.g] over the entire range of blend compositions. Addition of Hytrel to the PAR/LCP blend decreased both dynamic viscosity and storage modulus over the normal processing temperature range. Further, it notably reduced the voids between the LCP domains and the matrix, and improved the mechanical properties. The optimum usage level of Hytrel proved to be 2 phr., INTRODUCTION Introducing an inorganic reinforcing fiber into an isotropic polymer is a common and important method of improving the mechanical properties of engineering plastics. However, this often brings about several [...]

A polyarylate Unitika U-Polymer 100 (PAR) was melt blended with a thermotropic liquid crystalline polymer (LCP) Vectra A950, and the processing-morphology-properties relations were investigated. Inclusion of LCP slightly reduced T(sub g) of PAR. The PAR/LCP blend with the LCP content higher than 50 wt% exhibited a noticeable yield stress, particularly in the vicinity of crystal-to-nematic transition temperature (T(sub cn)). LCP lowered the blend viscosity above T(sub cn), and seemed to play a role as processing aid. The tensile strength of the blends was increased with increasing spin draw ratio and level of LCP, and the spinning temperature influenced tensile strength. The relaxation behavior under dynamic shear and resultant blend morphology based on WAXD and SEM analyses are discussed as well.